Preparation of 2,2&#39;-bipyridyls

ABSTRACT

IN THE PREPARATION OF 2,2-BIPYRIDYL OR ALKYL-SUBSTITUTED 2,2&#39;&#39;-BIPYRIDYLS FROM PYRIDINE OR ALKYLPYRIDINES IN CONTACT WITH HOT RANEY NICKEL CATALYST, THE OPTIMUM YIELDS ARE OBTAINED WHEN THE RANEY NICKEL IS PREPARED FROM NICKEL-ALUMINUM ALLOYS CONSISTING ESSENTIALLY OF BETWEEN 52 AND 56% OF NICKEL AND BETWEEN 48 AND 44% OF ALUMINUM.

3,822,279 PREPARATION OF 2,2'-BIPYRIDYLS John Anthony Joy and DavidCyril Marshall, Manchester, England, assignors to Imperial ChemicalIndustries Limited, London, England No Drawing. Filed June 12, 1972,Ser. No. 261,993 Int. Cl. C07d 31/42 US. Cl. 260-296 D 7 Claims ABSTRACTOF THE DISCLOSURE In the preparation of 2,2-bipyridyl oralkyl-substituted 2,2'-bipyridyls from pyridine or alkylpyridines incontact with hot Raney nickel catalyst, the optimum yields are obtainedwhen the Raney nickel is prepared from nickel-aluminium alloysconsisting essentially of between 52 and 56% of nickel and between 48and 44% of aluminium.

This invention relates to an improved process for the preparation of2,2'-bipyridyls and an improved nickel catalyst for use in this process.

2,2-bipyridyls may be prepared by contacting hot pyridine oralkylpyridines with nickel catalyst obtained by digesting a 50:50nickel-aluminium alloy with aqueous a a 1.

It has now been found that nickelaaluminium alloys containing a range ofhigher proportions of nickel are of advantage in that by digestion withaqueous alkali they afford nickel catalysts which give improved yieldsof bipyridyls from pyridines.

According to the invention there is provided a nickelaluminium alloyconsisting essentially of between 52 and 56% of nickel and between 48and 44% of aluminium.

According to the invention there is also provided a nickel catalystobtained by digesting with aqueous alkali a nickel-aluminium alloyconsisting essentially of between 52 and 56% of nickel and between 48and 44% of aluminium.

According to the invention there is further provided an improved processfor the preparation of 2,2'-bipyridyls which comprises contacting hotpyridine or an alkylpyridine with catalyst obtained by digesting withalkali a nickel-aluminium alloy consisting essentially of between 52 and56% of nickel and between 48 and 44% of aluminium.

As alkylpyridines there may be mentioned lower alkylpyridines especiallyu-, 8- and 'y-picolines, but ethylpyridine and pyridines containinghigher alkyl substituents may be used. Both tat-positions of thepyridine should not be substituted.

The pyridine or alkylpyridine may be contacted with the catalyst in anyconvenient manner at a temperature suitably between 50 and 150 C., andpreferably above 80 C., but it is preferred to adopt the procedure ofspecification No. 897,473 which corresponds to US. Pat. 3,053,846 inwhich liquid pyridine is percolated continuously through the catalystthus removing the bipyridyl as it is formed. The bipyridyl may then beisolated by any convenient method, for example vacuum distillation or byfractionation and recrystallisation of residues.

The pyridine or alkyl pyridine is preferably desulphurised by passage atan elevated temperature over a Raney nickel catalyst followed bydistillation.

The preferred nickel-aluminium alloy contains about 53% of nickel. Thenickel-aluminium alloys may be prepared in any conventional manner, forexample heating a mixture of nickel and aluminium in the appropriateproportions to a temperature of about 1600 C. for 16 hours under aninert atmosphere such as nitrogen. For preparation of the catalyst thealloy may be broken down United States Patent to a powder, suitably fineenough to pass a 60 mesh sieve, and digested with alkali and then washedwith Water in the manner conventional for the preparation of Raneynickel catalyst from the 50:50 nickel-aluminium alloy.

The invention is illustrated but not limited by the following Examplesin which all parts and percentages are by weight unless other-wisestated.

PREPARATION OF ALLOY Nickel shot and aluminium metal in the appropriateproportions are heated in an alumina crucible at 165 0 C. under anitrogen atmosphere for 16 hours and then cooled to room temperatureover 7 hours. The alloy is removed from the crucible and broken down bycrushing and grinding to a powder passing a 60 mesh sieve.

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PREPARATION OF CATALYST 12.5 parts of alloy powder are digested with asolution of 22.5 parts of potassium hydroxide in 72 parts of water at 78C. for 2 hours. The nickel catalyst obtained is washed by decantationwith water until free from alkali.

PREPARATION OF 2,2-BIPYRIDYL 6.5 parts of catalyst prepared as describedabove are placed in a fixed bed reactor held at a temperature of C.Pyridine at a rate of parts per hour is percolated for 74 hours throughthe catalyst bed from above. The treated pyridine is fractionated togive a distillate of pyridine and a residue containing 2,2-bipyridylwhich is purified by crystallisation from light petroleum. The pyridinedistillate is reused directly in the process.

The pyridine used above is commercial 2 pyridine which has beendesulphurised by several passes through a bed of Raney nickel catalystat a temperature of 110 C. and distillation. Omission of thedesulphurisation process leads to lower yields of bipyridyl. During thisdesulphurisation process a little bipyridyl is formed but this is notincluded in the yields given below.

The yields of 2,2'-bipyridyl obtained by the use of catalyst fromvarious nickel-aluminium alloys are listed below.

Proportion of nickel in alloy (percent):

Parts of 2,2'-bipyridyl per 100 parts of nickel 1. A process for thepreparation of 2,2-bipyridyl or a lower alkyl-substituted2,2'-bipyridyl, provided with both tat-positions are not substituted,which consists essentially of contacting hot pyridine or analkylpyridine with a nickel catalyst obtained by digesting with aqueousalkali a nickel-aluminium alloy consisting essentially of between 52 and56% of nickel and 48 and 44% of aluminium.

2. A process as claimed in Claim 1 wherein the nickelaluminium alloyconsists essentially of 53% of nickel and 47% of aluminium.

3. A process as claimed in Claim 1 in which the pyridine oralkylpyridine is at a temperature between 50 and C.

4. A process as claimed in Claim 1 in which the pyridine oralkylpyridine is at a temperature between 80 and 150 C.

3 I 4 5. A process as claimed in Claim 1 in which the pyri- 7 ReferencesCited 311cc :tra lzilzylpyridine is percolated continually throughUNITED STATES PATENTS 6. A process as claimed in Claim 1 in which thepyri- 3,697,534 10/1972 Waddan et 260295 D dine or alkylpyridine isfirst desulphurised by passage through a bed of Raney nickel catalystfollowed by dis- 5 ALAN ROTMAN Pnmary Exammer tillation and subsequentlycontacted with the said digested U S cl X R catalyst. 252 4 I D 7. Aprocess as claimed in Claim 1 in which the alkyl substituent is methylor ethyl. 10

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3'822'279 Dated July 1 1974 V Inventor(s) JOHN ANTHONY JOY ET AL.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Please add the following to the front page format after theserial'number:

--Claims priority, application Great Britain,

July 15, 1971, 333l0/7l- Signed and sealed this 24th day of June 1975.

(SEAL) Attest:

C. ITARSHALL DANN Commissioner of Patents and Trademarks RUTH C. MASONAttesting Officer F ORM PO-lOSO (10-69) USCOMM-DC 60376-P69 U 5.oovnmutm IRINYING OHICE use 0-366!!

